Fuel control system for internal-combustion engines



De.1s,1945. F, G, BOLLO TAL 2,394,291

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) I l I F. G. BOLLO ET AL Filed Jan. 2, 1945 I'lI FUEL CONTROL SYSTEM FOR INTERNAL-COMBUSTION ENGINES I I I I I I I I Dec. 18, 1945.

Patented Dec. 18, 1945 UNITED STATES PATENT ol-rlcEV FUEL coN'rRoL SYSTEM AFoa INTERNAL- coMUs'noN ENGINES Francis G. Bollo, Berkeley, and John R. Tomlinson, Walnut Creek, Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware n Application January 2, 1945, Serial No. 571,067

10 Claims. (Cl. 12S- 119) l will be understood from the following description taken with reference to the attached drawings,

wherein: f

Fig. 1 is a diagram'showing the general arrangement of the units forming the system of the present invention Fig. 2 is a chart diagram showing the relationv between the exhaust temperature of a spark ignition-type engine and the fuel-air-ratio of the mixture supplied Athereto by the fuel-metering means;

Fig. 3 is a diagram of self-balancing measuring bridge adapted for use in the present system;

Fig. 4 is a diagrammatic detail of another embodiment of a self-balancing measuring bridge;

Figs. 5 and 6 are diagrams showing diierent embodiments of the timing or cycling means of the present system;

Fig. "I is a diagram of the reversing relay means of the present invention;

Figs. 8 and 9 are diagrams showing variations of the system of Fig. 1.

Fig. 10 is a diagram of a latch-in reset relay which may be used in combination with the timing and reversing relay units of the present system.

For purposes of simplicity, the control system able to the operator, a manual adjustment of the fuel-air ratio between values determined by the setting of the automatic carburetor is not practicable. V

It has been found that the combustion temperature of internal combustion engines of the spark ignition type, as determined, for example, by measuring the temperature of exhaust gases, varies with the fuel-air ratio of themixtures supplied to said engines, the maximum temperavture being developed at fuel-air ratios which give the b est or very nearly the best engine fuel economy. Sharplylower exhaust temperatures result from relatively small changes in fuel-air ratio in either direction from this desired value.

Fig. 2 givesexhaust gas temperature and specie fuel consumption values plotted against fuelair ratios for two typical engine performances.

' .In both cases, a sharply defined temperature peak of the present invention will be described mainly l vwith regard to aircraft engines, it being understood that said system is not limited to application in such engines and may as well be used with other engines of the land or marine transportation types, or with stationary installations. f

Modern internal combustion engines of the spark ignition type usually employ automatic fuel metering means, such for example as automatic carburetors or fuel injectors, for supplying to the engine a fuel-air mixture at predetermined fuelair ratios to iit particular operating conditions.

This type of control, however, does not always provide the optimum mixture for each operating condition, particularly during relatively long periods of stable operation, where the mixtures are apt to -be richer than desired for best economy. Since an accurate and instantaneous measurement of the fuel consumption rate is rarely availprevails at, or quite close to, the fuel-air ratio giving maximum economy. The points marked A. L. and A. R. refer to values obtained with theAutomatic-Lean and the Automatic-Rich settings of the automatic carburetor. It will be seen that neither of these settings gives the most economical operation, which in both cases lies outside of the range provided by the automatic carburetor.

It is therefore an object of this invention to provide a control system for automatically maintaining the setting of the fuel-injector means of an internal-combustion engine at its most economical fuelair ratio, said setting' corresponding to approximately the highest temperature developed bythe engine as said fuel-air ratio is varied.

It is also an object of this invention to provide for vthe purpose described a control system adapted to actuate the fuel-metering or fuelinjector means regulating the fuel-air ratio of the mixture supplied tothe engine for combustion, said actuation being eiiected periodically or cyclically, that is, at predetermined time intervals.

It is also an object of this invention to provide a system adapted to effect said actuation of the fuel-metering means in one direction throughout operative portions of consecutive cycles as long as the temperature of the engine, and more particularly its exhaust temperature, does not change in a negative direction, that is, toward lower temperature, and to reverse the direction of said actuation when the temperature of the engine decreases.

It is also an object of this invention to provide a system adapted toi actuate the fuel-metering means soas to leilect a substantially continuous smooth or-linear change in the fuel iiow to the engine.

Other objects of the present invention will be v clear from thefiollowing description thereof.

Referring tothe diagram of Fig. 1, the system of the present invention comprises the following 4elements suitably cooperating with each other by be used, if desired, to effect such actuation. Al-

though .the terminals of the various. electrical y units of the diagram are shown in all Acases to be connected to each other by separate or double l leads, the second lead may be eliminated whereever suitable by grounding the appropriate terminals, as will be understood by those familiar with electric circuits, and as shown for purposes of illustration at 38 and 33a only in Fig. 3.

will cause the -motor 3l to rotate in the proper direction to re-set and rebalance the measuring circuit. The operating current for the vmotor and the electronic circuit is supplied from leads and I2. If the galvanomete;` has deected in response to a 'change of thermocouple voltage produced by an increase of exhaust temperature, the motor 315 is actuated in one direction by a current pulse received from the bridge circuit through a lead 35.v If the galvanometer has deiiected in response to a decrease of temperature,

- the motor is actuated in the other direction by a Couple.

The temperature-responsive element or thermocouple 2 is operatively installed in thev engine in any suitable location under the effect ofthe Aengine temperatures, for example in a cylinder head. It is, however, preferred to install said thermocouple in the stream of the exhaust gases of the engine, forfexample in the exhaust pipe or manifold,1sinc`e this position, rst, insures the quickest response of the` thermocouple to engine temperature changes; second, eliminates the effect thereon of extraneous factors, suchl as the coolant for .the engine; and third, makes the thermocouple responsive to the temperatures of the engine as a unit, rather than to those of the inyoke |36 about its axis |31. On the next turnv dividual cylinders. Furthermore, the exhaust gas.

besides giving the quickest temperature response, also gives the largest temperature change.

The thermocouple 2 is connected by means of leads 2| and 22 to the self-balancing measuring bridge orpotentiometer unit 3, which, as stated above, may be provided with its own power supply, or may receive its operating current from the power source by means of leads and I2.

The unit 3 'preferably'comprises a self-balancing' potentiometer, such,y for example, as that manufactured by the Brown Instrument Co.. as described in their bulletin No. 15-4 (1942) or by the TagliabueV Manufacturing Company, as described in" their catalog No. 1101E (1939), or by` the Leedsj and Northrup Company, as described in their catalog No. 33-161 (1940), etc.

The construction and operation of self-balancing potentiometers involving the use of a reversible motor, such, f or example, as the Brown'or.

the Tagliabue potentiometer, lforms no part of this invention. and will be briefly outlined here with regard to the diagram'of Figure 3 only as far as necessary for its application to the present system.

`The voltage of the, thermocouple 2 is balanced in a bridge'circuit 30; comprising a 4pointer or a mirror-type galvanom'eter l3|, against the constant voltagev of a standard cell 32. Arw change in the voltage .of the thermocouple will unbal ance the bridge circuit and cause a deflection ot "the galvanometer, which, by mechanical 'or photo- 'd lelectric means involvinganelectronic circuit 33,

current pulse received from the bridge circuit through a lead 33. According to the present invention, the lead 36 is'tapped by a lead 3l connected to the timing unit 4., It will therefore be seen that it is essential for the present invention that electric ycurrent be supplied from the selfbalancing potentiometer to the timing unit only at such times as the potentiometer is being rebalanced to a new setting in response to a decrease of the temperature aiecting the thermoa constant speed undirectional motor |36 drives a shaft |30 carrying cams |32 and |33. An unbalanced condition of the measuring bridge circuit causes the galvanometer needle |3i to deflect from its normal position. The setting levers |35, by closing about the 'galvanometer needle in its ofi-center position, tilt the normally horizontal of the shaft |30, one of thecams |32 orV |33 contacts .the tilted yoke |33 and returns it to its horizontal position, thus moving suitable resistor wire contacts not shown, and rebalancing the measuring circuit. If the galvanometer needle deiiects in the other direction, the yoke |36 is likewise tilted the other way,and is returned to its normal position by contact with the cam |32, thus effecting arebalancing of the measuring bridge circuit in an opposite sense or direction.

. According to the present invention, a switch or pair of contacts |33a 'and' |36a are arranged d to close everytime that the potentiometer circuit rebalances itself after a change of conditions resulting from a decrease of temperature. Thus, assuming that a decreased thermocouple current resulting from a lower temperature vcauses the galvanometer needle to travel to the right, whereby the right-hand arm of the yoke |36 is tilted upwards as shown in the drawing, to be reset by the cam |33, the contacts |33a and |36a may, for example, be attached. to said arm and cam respectively, whereby the circuit of the wire 31 will be closed only under the conditions dened above, and the arrangement'of Fig. 4 will operate in a manner similar to that tiometers vbesidesthose described with regard to d Figs. 3 and 4, may be used as long as such arrangement results in achieving the desired object of supplying a current pulse to the cycling unit 4 only at such times as the potentiometer unit rebalances itself to a lower temperature.

The timing` or l'cycling unit 4 may consist of any arrangement ,suitablel for periodically or cyclically-actuating switches 4| and 42, lwhich vdevices.

switches 4| and 42 are opened and closed may.

serve to close and to open the circuits of the reversing relay unit 5 and of the armature of motor 6, respectively. For example, as shown in Fig. 5, a constant speed unidirectional motor 44, receiving its power from leads vI3 and I4, may drive through any suitable gear reducer mechanism 49, a cam 40 provided with projections 41 adapted to contact the spring-loaded, normally open switch members 4| and 42, thus cyclically closing and opening the desired circuits. If the self-balancing potentiometer of Fig. 4 is used, the motor 44 may be dispensed with, and the cam 40 may be directly mounted'on or driven by the shaft |30, thus synchronizing the two The constant frequency at which the be controlled for purposes to be described hereinbelow, in any desired way, for example by adjusting the speed of the motor 44, by adjusting the gear reducer 4mechanism 49, or by varying the size, spacing ornumber of the -cam projections 41, said projections being for this purpose adjustably held by means of removable bolts 48 in a slot 46 in the cam body.

It is evident that the object of the timing unit, which is yto open and to close at adjustable constant time intervals the circuits of the armature of the motor 6 and of the reversing relay unit 5,

may be achieved by means other than cams, for

example by means of mechanical or electronic commutators. Fig. 6 shows by way of illusutration an arrangement wherein an electronic commutator 60, having a circuit such, for example, as disclosed in application Ser. No. 410,010 filed September 8, 1941, by D. S. Muzzey et al, provides periodic pulses to solenoid coils 6| and 62,

thus lifting the magnetic armatures or switchl members 4 la and 42a and closing the desired cir-r cuits.

The reversing relay unit 5, whose purpose is to lreverse the direction in which the fuel-metering means are being actuated, for example by reversing the polarity of the eld of the reversible motor E in response to current pulses received or to decrease the fuel-air ratio of the mixture supplied to the engine by the fuel-injector device 1. The rod 21 has also attached thereto a handle and locking device 29, which, in combination with the torque-limiting clutch 25, permits the operator to override the control action of the present `system and to determine the setting of the fuel- Y metering means manually at such times when translated into a change of the potential of the through from the measuring bridge unit through...l

the timing unitv switch 4|, acts to retract a pawl 1| against the action of a spring 12. The pawl 1| rotates a ratchet wheel 13, which drives a cam v14 through 45 degrees upon each retraction of the pawl.1|. The cam 14 actuates spring loaded conductor members 1 5 and 16, connected to theleads 23 and 24 by means of leads 11 and 'I8 respectively, into contact with leads 80 and 8| in the position shown in the drawingsor with leads 82 and 83 when the cam is displaced by 45 degrees from the position shown in the drawings. The leads 80, 8|, 82 and 83 being connected to the field 85 of the reversible motor as shown in Fig. 7, the direction of thecurrent iiow through said iield, .and therefore the direction of rotation of the reversible motor B, will be reversed at each thermocouple 2, and causes the self-balancing measuring unit 3 to readjust itself to this new condition. If this change is caused by an' increase of temperature, showing that the fuel-air ratio of the fuel injector 1 is either already set at its optimum value, or is being adjusted toward said optimum value, the automatic rebalancing of the measuring unit 3 produces no current pulse in the leads 31 and 38 as already stated in ,connection with the description of Figs. 3 and 4.

' If, on the other hand, this change is caused by a decrease of temperature, showing either that the fuel-air ratio is improperly set, and is being adjusted inthe incorrect direction whereby a mixture which is already too`rich is made still richer, or' a mixture which is too lean is made still leaner, the automatic rebalancing of the measuring unit 3 will produce a current pulse which is applied through the leads 31 and 38, connected to the timing unit 4 and to the reversing relay unit 5.

The function of the cycling unit 4 -is to open and to close at predetermined and adjustable time intervals the switches 42 and 4|. The closing of the switch 42 will energize both the leld and the armature of motor 8 throughout an operative portion of each cycle of the timing unit and cause a rotation of said motor, in one direction or the other, depending on the` way in which the iield is connected, every time the switch 42 closes;

The closing of the switch 4 l, if no current pulse has been delivered by the self-balancing measuring unit 3, will produce no effect. The eld of the motor 8 will therefore not be reversed, and said motor will rotate in the same direction as on the precedingclosure cycle of the unit 4. If, howevena current pulse has been delivered by the self -balancing unit 3, the closing of the switch; 4| will energize the reversing relay unit 5, and will reverse the eld of the motor 6, thus'causing said motor to rotate in a direction opposite to that of the preceding cycle.

Since self-balancing potentiometers of the type illustrated inr'ig. 3 operate on very small increments of time, the synchronization between the operation of units 3 and 4 is assured by the fact that the unit 3 rebalances several times during each closure of the switch 4|.

shown on pages 1415F of their catalog of July 1942. Likewise a similar relay 9 may be connected into the circuit of the present system as show n Sincev any even number of operations of the reversing unit for purposes of illustration in Fig. 10. A pulse lll, which maintains the switch |12 closed, thus insuring only one operation of the reversing relay unit per cycle, independently of the number of pulses transmitted through leads 31 and 36 during a single closure of the switch 6|. The timing .unit dB is provided with an additional switch 43,

similar in construction and operation to the switches M and d2, as'described hereinabove with regard to Fig. 5. Switch d3 is adapted to remain open during the closure of switch 4|, and to close briefly after switch 4| opens. The closing of switch i3 short-circuits and de-energizes the hold-up coil |12, thus opening the switch |12 and resetting the-relay 9 for operation during the next cyclefgg-In the case of self-balancing potentiometersf the type illustrated in Fig. 4, this synchronization may be achieved by operating the units 3 and 4 from a single motor shaft, as already described with regard to Figs. 4 and 5.

The object of the timing unit li is to give the system time, on each cycle, to react to a change of temperature due to a change of fuel-air ratio effected during the preceding cy'cle, and also 'to eliminate the effect on said system of extraneous temperature changes due to causes other than fuel-air. ratio changes, such as variations in the temperature of the air, changes of level of anaircraft engine, etc. Taking into consideration the mechanical and electrical inertia of the various components of the system, the timing unit of said system should be adjusted, during calibrathe size, shape or spacing of the cycling unitv cams, by adjusting the electrical constants of an electronically op'erated timing unit, etc.

It will therefore be seen that the present automatic system permits the control of the fuel-air ratio, so as to maintain it at the point of the highest engine temperature corresponding to the most economical operation, under any possible set of conditions.

Thus, considering'all possible sequences of events during a cycle A and an immediately consecutive cycle B, the foilowing cases are possible:

1. If the fuel-air ratios/is too low, and the fuelmetering. has been actuated during cycle A-to further deorease'it, the engine'temperature will decrease in the time interval between' cycles A and'B, the unit 3 will deliver a pulse to the timing device, and the closure of switch 4| on cycleB will reverse the eldoflthe motor 6, whereby the 'closure of switch 42 on said cycle B will actuate the motor and the fuel-metering means in' a'direction opposite to that-of cyclel A.

n2. If the fuel-air ratio is too low, but the fuelmetering means have, already been actuated on cycle A in the properdir'ection to correct this ratio, the temperature of the engine will increase in the time interval between, no pulse will be supplied by the unit. 3, andthe closine of switch 4| on cycle B will remain inoperative, thus permit- 'ting the closureof the switch 42 to actuate the fuel-meteringv means in the same direction as on cycle A.

- 3'. If the fuel-air ratio is too high, and the fuelmetering means have been actuated to further increase it during cycle A, the direction of said actuation will be reversed during cycle B in the manner described in case 1.

,4. If the fuel-air ratio is too high, but the fuelmetering means have been actuated in the proper direction during cycle A, they will be actuated in the same direction during cycle B, as described in case 2.

When the maximum engine temperature, that is, the optimum operating condition is reached, i..

the system will hunt within a very narrow rangea from one side to the other of the mixture ratio corresponding to said maximum temperature. The effect of this hunting can be made negligible by adfusting the various timing, transmission and gearing factors 4so as to limit the single cycle change in fuel-air ratio to a small value.

Although the present system has been described hereinabove as involving the operation of a 're- ,versible motor 6, it will be understood that'this' invention is in no way limited to the use of such motor, but may comprise any combinationof electrical or mechanical means capable of periodically actuating the fuel-'metering element controlling the fuel-air ratio in such a manner as to modify said ratio in accordance with the indications of the temperature-responsive element. Thus, as diagrammatically shown in Fig. 8, a unidirectional, intermittently or cyclieally operating motor 6a may be used instead of the reversing motor 6, the function of the reversing relay unit 5a consisting in this case not in reversing the eld of motor 6, but in actuating a reversing gear box Ilil, thereby reversing the direction of rotation of a worm gear |03, connected to the shaft of the motor 6a through said reversing gear box, and causing a traveling nut |05, actuating the fuelmeteringglever 26, to move in the opposite direction. An amplifier |06 may be insertedv in the -circuit of Fig. 8, as also in the circuit of Fig. 1, to

increase the power of the pulses transmitted to the reversing relay unit.

Likewise, a unidirectional, continuously operating motor 6b may be used, for example by inserting a, magnetically operated clutch |01 in the drive between the motor 6b and the worm gear |03 so as to transmit the rotational motion of the motor 6b to the worm gear |03 only during the operative portion of each. cycle. The wiring of the circuit of Fig..8 can in this case be modified as shown in Fig. 9. l

While the present invention has been described hereinabove with regard to preferred embodimerits thereof, it is to be understood that suitable changes in construction, combination and arrangement of parts may' be made without departing from the spirit or the scope of the invention as defined in the appended claims-. It is obvious air ratio of the mixture su tem comprising means for cyclically changing said fuel-air ratio, and means responsive to the temperature of the engine for controlling the direction of said change.

2. For use in combination with a spark ignition type engine having fuel metering means adapted to be selectively actuated in opposite directions vto effect corresponding opposite changes in the fuelair ratio of the mixture supplied to said engine, a

system comprising means for actuating said fuel metering means at constant time increments to change said fuel-air ratio, and means responsive to the temperature of the engine for controlling the direction in which said fuel metering means are actuated.

3. In combination with aspark ignition type engine having fuel metering means adapted to be selectively actuated in opposite directions to effect corresponding opposite changes in the fuel-air ratio of the mixture supplied to said engine, a

system comprising time-responsive means for cyclically actuating said fuel metering means to change vsaid fuel-air ratio, and means comprising a thermocouple responsive to the engine exhaust temperature for controlling the direction in which said fuel metering means are actuated.

4. In combination with a spark ignition. type engine having fuel metering means adapted to be selectively actuated in opposite directions to effect corresponding opposite changes in the fuelfor transmitting said current pulses to said relay measuring bridge means adapted to translate said potential variations into current pulses, means for selectively transmitting current pulses responsive to temperature decreases to saidl relay means throughN said timing means during the operative portion of a cycleof said timing means, whereby said relay means are energized and the fuel metering means are actuated during the operative portion of said cycle in a direction opposite to that of their. actuation during the preceding cycle.

7. The system of claim 6, comprising adjustable means for regulating the frequency of the timing means.

8. The system of claim 6, comprising adjustable means for regulating the magnitude o f the operative portion of a cycleof the timing means.

9. In combination with a spark ignition type engine having fuel metering means adapted to regulate the fuel-air ratio of the mixture supplied to said engine, a vsystem comprising a reversible motor capable of selectively actuating said fuel metering means in one direction for increasing said fuel-'air ratio, and in theother direction for decreasing said fuel-air ratio, constant frequency timing means adapted to energize said motor throughout a predetermined operative portion of a cycle of said timing means, relay means adapted to reverse the direction in which` said motor rotates upon energization, thermocouple means adapted to produce a varying potential in response to engine exhaust temperature changes, measuring bridge means electrically connected to said thermocouple'means and adapted to be auto.-

-matically re-balanced against said potential variations, said measuring bridge'means being provided with selective means for producing unidirectional current pulses upon each re-balancine.r occurring in response to a decrease of exhaust temperature, and means for transmitting said current pulses to said relay means through said means, whereby said relay means are energized"v to reverse the direction vin which the fuelmetering means are actuated.

.5. In combination with a spark ignition type engine having fuel metering means adapted to be selectively actuated in opposite directions to eifect corresponding opposite changes in the fuelair ratio of the mixture supplied to said engine, a

system comprising thermocouple means exposed to the temperature -of the engine, and timing means adapted to actuate the fuel metering means at constant time intervals, said timing means being responsive to said thermocouple means for reversing the direction in which said metering means are actuated upon a decrease of the engine temperature during the time interval between two consecutive actuations of said fuel metering means. i

6. In combination with a spark ignition' type engine having fuel metering means adaptedto be -selectively actuated in 'opposite directions to effect corresponding opposite changes in the fuellied to said engine. a system comprising consta t frequencytiming means adapted to actuate said fuel metering means. to change the fuel-air ratio throughout a predetermined operative portion of each cycleof -I said timing means, relay means adapted toreve'rse the direction in which said fuel metering means are actuated, thermocouple means adapted to produce variations of potential in response to a change of the engine exhaust temperature.

timing means during the operative portion of a cycle of said timing means, said relay means being adapted to reverse the direction of rotation of said motor upon each consecutive energization by 'said unidirectional pulses.

10. For use in combination with a spark ignition type engine having fuel metering means adapted to be selectively actuated in opposite d1- rections to effect corresponding opposite changes y -a decrease oi' temperature into. current pulses .and to apply said pulses to the relay unit through the Y timing unit, said timing unit being adapted to actuate said fuel metering means at predeter- -mined constant time intervals and to transmit said current pulses from the measuring. bridge unit to the relay unit. and said relay unit being adapted to 'reverse the direction of, actuation of said fuel metering means in response to said pulses, thereby changing Said fuel-air ratio.

FRANCIS G. BOLLO. JOHN R. TOMLINBON. 

